MIT scientists create new method of sorting cells using sound waves

Researchers from
MIT, Carnegie Mellon University and Pennsylvania State University have developed a novel technique of separating cells with the use of a gentle sound wave. The technique could potentially be used to screen a patient’s blood, allowing medical practitioners to isolate rare tumor cells synonymous with diseases such as cancer.
The concept behind the new method involves placing two acoustic transducers on either side of a microfluidic device. Each transducer creates a sound wave, and when these waves impact on each other they combine to form a single static wave across a fluid channel running through the device.
As the abnormal cells pass through the fluid channel and hit the pressure points created by the sound wave, they are pushed to the side of the channel, away from the mass of ordinary cells accompanying them through the fluid. The amount of deviation created by the wave depends on cell characteristics such as size and density.
One of the benefits of using sound to differentiate cells is that it makes the separation process very gentle, posing essentially no risk to the cell, especially when compared to current methods of separation using chemical tagging or exposing them to stronger mechanical force – both of which could be harmful to the cells.

Previous experiments utilizing the sound wave method were ineffective, placing the sound barrier horizontally, thus only requiring the cells to pass through a single sound pressure point and limiting the amount that the cell deviates from the center of the channel. The new system pioneered by the team from MIT builds on this method, but instead orientates the sound wave at a slant. This subtle modification causes the cell to pass through multiple sound pressure points as it makes its way through the channel, causing it to drift to the outside in a much more obvious fashion.
Originally the device was tested with beads measuring between 7.3 and 9.9 microns. The results of the test were overwhelmingly positive, with the device separating the differing beads with 97 percent accuracy. The team then went on to test the ability of the device to detect abnormal cells, by having it separate breast cancer cells (with a typical size of 20 microns) from white blood cells (12 microns). Once again the device performed admirably, picking up 71 percent of the cancer cells.
Furthermore a computer simulation was created, allowing the team to ascertain what a cell’s path would be through the sound waves when placed at different angles, factoring in the cell’s density, compressibility, and size. The information attained from the simulation will allow the team to tailor the device to separate out specific cells based on their normative characteristics.
Looking to the future, the team have filed for a patent on the device, and hope to test the technique further on blood samples extracted from cancer patients in order to determine whether it will continue to perform with a high level of accuracy in a real-world situation. If the tests prove to be successful, the separation method could prove to be a safe, and efficient tool for doctors in determining the spread of a disease such as cancer.
A paper on the teams work is available in the journal Proceedings of the National Academy of Sciences.
The video below displays the device at work, courtesy of MIT.
Source: MIT

 

 

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Unique polymer soaks up CO2

Hydrogen may hold promise as an alternative to fossil fuels, but there’s still a huge petrol-producing infrastructure in place, and not many service stations offer hydrogen refills yet. That’s why some scientists are exploring a bridging technology known as the integrated gasification combined cycle (IGCC) process, for converting fossil fuels into hydrogen. Along with hydrogen, though, carbon dioxide is also a byproduct of the IGCC process, which must be dealt with. Fortunately, scientists from the University of Liverpool have developed a polymer that soaks up that CO2 for use in other applications.

The adsorbent organic polymer is described as being brown and sand-like, and consists of a linked network of carbon-based molecules. Its creation was inspired by polystyrene, which is able to adsorb small amounts of CO2 from the atmosphere. The new polymer likewise adsorbs CO2 but does so much more effectively, swelling up to contain the carbon dioxide in “micropores” between its molecules.

This swelling/adsorbing action takes place when the material is exposed to high-pressure environments, such as would be experienced in the IGCC process. When the pressure subsequently drops to normal levels, however, the polymer releases the CO2. The gas could then be harvested for use in carbon-based chemical products.

Along with its application in IGCC, the polymer could conceivably also be used to help “scrub” carbon dioxide from smokestack emissions. Whileother materials are already used for this purpose, the polymer should be particularly well-suited to it. This is largely because unlike some of those other materials, it doesn’t adsorb water vapor. Doing so would clog its pores, thus making it less effective.

It’s also said to be relatively inexpensive to produce, plus it’s very robust – it’s reportedly able to retain its functionality after being “boiled in acid.”

The researchers’ findings were presented today in San Francisco, at the 248th National Meeting & Exposition of the American Chemical Society.

Source: ACS

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Scientists create a “water tractor beam”

If you’ve ever tried to retrieve an object that’s floating away in a lake or the ocean, then you’ll know how frustrating it can be, trying to draw that item towards you. According to research recently conducted at The Australian National University (ANU), however, it’s possible to move such objects in whichever direction you wish – as long as you can generate the right type of waves.

The research team experimented with a table tennis ball floating in a wave tank. By precisely manipulating the size and frequency of three-dimensional waves created by a wave generator, they were able to keep the ball in place, move it away from the generator, or even towards it – in the case of the latter, the ball was actually moving against the waves that were traveling out from the generator.

Although the scientists did establish that the waves generate flow patterns along the surface layer of the water, the actual mathematics behind the phenomenon are still not understood. “It’s one of the great unresolved problems, yet anyone in the bathtub can reproduce it,” said project leader Dr. Horst Punzmann. “We were very surprised no one had described it before.”

It is hoped that if scaled up, their findings could be used in applications such as containing oil spills, retrieving drifting watercraft, or better understanding rip tides, in which swimmers are drawn away from the shore even though the waves are moving towards it.

A paper on the research was published today in the journal Nature Physics. The wave tank experiments can be seen in the video below.

Source: Australian National University

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Questions no one knows the answers to .

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PARS tech turns bodies transparent

Ordinarily, when scientists want to see specific cells within a piece of biological tissue, they first have to remove that tissue from the body, slice it very thin, then examine those two-dimensional slices using a microscope. Imagine, though, if the tissue could be made transparent – seeing tagged cells within it would be sort of like looking at three-dimensional bubbles inside an ice cube. Well, that’s just what a team at Caltech have done using a technique known as PARS, or perfusion-assisted agent release in situ.

PARS is an extension of the Caltech-designed CLARITY technique, which has previously been used to render the brains of lab mice transparent. It does so via a process in which the brains are infused with detergents that dissolve lipids – lipids are molecules within cells that provide them with structural support, but which also block the passage of light through those cells. A clear polymer hydrogel is additionally introduced, to replace the now-lacking structural support.

This is also the principle behind PARS, although in its case, the detergents and hydrogel are quickly diffused throughout a dead mouse’s entire body via its circulatory system. After the liquids are injected into its bloodstream, most of the animal’s major organs become completely clarified within two to three days, with the brain and the rest of the body taking two weeks.

Molecules such as DNA are left intact, and cells of interest can either be pre-tagged with genetically introduced fluorescent proteins, or marked with dyes after the “tissue-clearing” process has been performed. In cases where it isn’t necessary to clarify the whole body, a variation on PARS known as PACT (passive clarity technique) can be used on individual organs within it. In either case, the cells can be imaged within the transparent tissue using standard microscopy techniques.

Along with its potential for use on animal models, the technology has already been utilized to view the distribution of individual tumor cells within a human skin tumor.

“I think these new techniques are very practical for many fields in biology,” said assistant professor of biology Viviana Gradinaru, who led the research. “When you can just look through an organism for the exact cells or fine axons you want to see – without slicing and realigning individual sections – it frees up the time of the researcher. That means there is more time to the answer big questions, rather than spending time on menial jobs.”

A paper on the research was recently published in the journal Cell.

Source: California Institute of Technology

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HOW DOES SUGAR AFFECT THE BRAIN SEE TO KNOW

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